Tag Archives: Palmer amaranth

Weed of the Month: Palmer Amaranth

  • Palmer AmaranthCommon name: Palmer pigweed
  • Scientific name: Amaranthus palmeri 1
  • Grass or broadleaf: Annual broadleaf
  • Native to the Southwestern desert regions of the United States, Palmer amaranth has expanded rapidly across the Southeast and can be found in multiple Midwestern states.1
  • Germination timing: Palmer amaranth emergence is from early May until mid-September. This long emergence period forces farmers to manage the weed throughout the year, unlike other summer annual weeds that are typically managed only through early summer.1
  • Competitiveness: Known as the most competitive and aggressive pigweed species, Palmer amaranth can lead to soybean yield loss up to 79 percent and corn yield loss up to 91 percent in some states. It also can significantly increase production costs.2
  • Palmer amaranth grows fast – as much as 2 to 3 inches per day – and commonly reaches 6 to 8 feet.2
  • Farm equipment, specifically combines, and wildlife can spread Palmer amaranth seed into new, previously uninfected fields.1

Fast facts

  • Palmer amaranth has dioecious reproduction, meaning plants are either male or female, which forces outcrossing and genetic diversity.1 This makes it more difficult to control.
  • Each plant can produce 100,000 or more seeds when it competes with a crop. In noncompetitive scenarios, each plant can produce nearly a half million seeds.
  • According to WeedScience.org, the first confirmation of glyphosate-resistant Palmer amaranth in Midwest corn, cotton and soybean fields occurred in Missouri in 2008.
  • To identify Palmer amaranth, look for smooth green leaves arranged in an alternate pattern that grows symmetrically around the stem. The leaves are oval to diamond-shaped. There may be a small, sharp spine at the leaf tip.2
  • Palmer amaranth seeds are small and thrive in no-till or minimum-tillage fields.1

Weed management tips1

  • Rotate crops: this allows farmers to use herbicides with additional modes of action in the field.
  • Practice deep tillage: this will bury the small Palmer amaranth seed below its preferred emergence depth.
  • Plant a cereal rye cover crop: this crop can provide a mulch that will suppress Palmer amaranth emergence.
  • Harvest heavily infested fields last: because machinery so easily spreads Palmer amaranth seeds from one field to another, consider harvesting fields or parts of field with infestations last to limit seeds to that area.

Resistance Statistics*

  • According to WeedScience.org, herbicide-resistant Palmer amaranth has been documented in corn and soybean fields in 24 states: Alabama, Arkansas, California, Delaware, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Michigan, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Wisconsin.

*Resistance confirmation does not include all weeds and may vary among different areas of each state.

Corteva Agriscience, Agriculture Division of DowDuPont, offers the following weed control solutions:

Corn

DuPont Cinch® ATZ herbicide
Durango® DMA® herbicide
Elevore herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system
FulTime® NXT herbicide
Keystone® LA NXT herbicide
Keystone® NXT herbicide
DuPont Realm® Q herbicide
Resicore® herbicide
SureStart® II herbicide

Soybean

Durango® DMA® herbicide
Elevore herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system
DuPont EverpreX® herbicide
FirstRate® herbicide
Sonic® herbicide
Surveil® herbicide
DuPont Trivence® herbicide

Additional information:

For more information, read these weed science resources:

Sources:
1Purdue University Extension 2013. Palmer Amaranth Biology, Identification, and Management. https://www.extension.purdue.edu/extmedia/WS/WS-51-W.pdf
2Minnesota Department of Agriculture 2018. Palmer Amaranth in Minnesota. https://mda.state.mn.us/plants-insects/palmer-amaranth-minnesota

®™Trademark of The Dow Chemical Company (“Dow”) or E. I. du Pont de Nemours and Company (“DuPont”) or affiliated companies of Dow or DuPont. Cinch ATZ, FulTime NXT, Keystone LA NXT and Keystone NXT are federally Restricted Use Pesticides. Cinch ATZ, Durango DMA, Elevore, EverpreX, FulTime NXT, Keystone LA NXT, Keystone NXT, Realm, Resicore, Sonic, SureStart II, Surveil and Trivence are not registered for sale or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Enlist Duo and Enlist One herbicides are not registered for sale or use in all states or counties. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use in Enlist crops. Always read and follow label directions. ©2018 Dow AgroSciences LLC

Weed of the month: Palmer amaranth

  • Palmer amaranthCommon name: Palmer pigweed
  • Scientific name: Amaranthus palmeri
  • Grass or broadleaf: Annual broadleaf
  • Commonly observed late spring through fall months and continues to emerge throughout the growing season — growing up to 3 inches per day in ideal conditions.
  • Known as the most competitive and aggressive pigweed species, Palmer amaranth can lead to corn yield loss up to 91 percent when allowed to compete with the crop throughout the growing season.1
  • Not only a threat to corn, season-long competition by Palmer amaranth at 2.5 plants per foot of row can reduce soybean yield by as much as 79 percent.1
  • Native to the Southwestern desert regions of the United States, devastation from Palmer amaranth has expanded across the Southeast and, recently, to the upper Midwest.
  • This invasive species has become one of the most significant weeds impacting cotton, corn and soybean production.

Fast facts from Jeff Ellis, Ph.D., field scientist, Dow AgroSciences

  • Palmer amaranth can adapt and quickly produce resistance genes to single-mode-of-action herbicides because individual plants are either male or female. This forces outcrossing and genetic diversity.
  • A single female plant can produce 600,000 seeds, which are rapidly spread through grain, seed, feed or equipment contamination.
  • Identifiable by its unique leaf shape, which is wide and ovate- to diamond-shape; Palmer amaranth leaves are commonly 2 to 8 inches long and a half-inch to 2½ inches wide.
  • Sometimes, the plants may show a white V-shaped watermark on the leaves. This watermark rules out other members of the pigweed family.

A fact that may surprise you …

  • Just how did an invasive desert plant make its way to the Midwest? Researchers believe Palmer amaranth was introduced to northern Indiana through manure from cattle that consumed seed-contaminated feed stocks from the South, such as cottonseed hulls. Farm equipment and wildlife also contribute to the spread of Palmer amaranth seed.

Resistance statistics*

  • According to WeedScience.org, herbicide-resistant Palmer amaranth has been documented in corn and soybean fields in 24 states: Alabama, Arkansas, California, Delaware, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Michigan, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Wisconsin.

*Resistance confirmation does not necessarily include all weeds in a population are resistant. Levels of resistance may vary in different areas of each state.

Tips for controlling and managing Palmer amaranth:

  • The key to mitigating Palmer amaranth is making control a priority before the weed emerges and addressing it when the plant is small. Given the threat Palmer amaranth poses to yield, growers should implement a season-long management plan, using residual herbicides with multiple modes of action to prevent Palmer amaranth seeds from spreading.
  • Tank-mix residual herbicides with postemergence herbicides to help avoid emergence issues later in the season. Layering residual products is important to control this weed, which germinates throughout the growing season.
  • Soybean farmers, especially, should always use residual herbicides to help control Palmer amaranth after crop emergence because there are few effective postemergence herbicide control options.

Tips for managing herbicide-resistant weeds:

Farmers in the Midwest and Midsouth are no strangers to some of the toughest weed species, such as: Palmer amaranth, waterhemp, ragweed and marestail. Implement these management best practices to help manage weed resistance issues during the season.

  • Develop an integrated weed management plan that delivers multiple modes of action throughout the season. The Enlist weed control system allows use of effective postemergence modes of action, including new 2,4-D choline, glyphosate and glufosinate in soybeans and new 2,4-D choline and glyphosate in corn.
  • Use full rates of the herbicides during applications. Do not use partial rates for any reason, including cost.
  • Spray when weeds are small. Although application can be challenging because of weather and other factors, timing is critical to achieve the best control.
  • Scout fields regularly to identify weeds when they are small and easy to control.

Dow AgroSciences weed control solutions:

Corn
SureStart® II herbicide
Resicore® herbicide
Keystone® NXT herbicide
Keystone® LA NXT herbicide 

FulTime® NXT herbicide
Surpass® NXT herbicide 
Durango® DMA® herbicide
Duramax® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system

Soybean
Sonic® herbicide
Surveil® herbicide
Durango® DMA® herbicide
Duramax® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system

Additional information:

Find more information using these weed science resources:
Palmer Amaranth In Minnesota — Minnesota Department of Agriculture
Palmer Amaranth Biology, Identification and Management — Purdue University Extension
Guidelines for the Identification and Management of Palmer Amaranth in Illinois Agronomic Crops — University of Illinois Department of Crop Science
Palmer Amaranth Identified in Nine Iowa Counties — Iowa State University Extension and Outreach/Integrated Crop Management

Sources:

1 Minnesota Department of Agriculture. 2017. Palmer Amaranth In Minnesota.
https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/palmeramaranth/palmeramaranthfs.aspx

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. FulTime NXT, Keystone LA NXT and Keystone NXT are federally Restricted Use Pesticides. Duramax, Durango DMA, FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore, Sonic, SureStart II, Surpass NXT and Surveil are not registered for sale or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore, SureStart II and Surpass NXT are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Enlist Duo and Enlist One herbicides are not registered for sale or use in all states or counties. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use in Enlist crops. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Always read and follow label directions. ©2017 Dow AgroSciences LLC

Weed of the Month: Palmer amaranth

  • Palmer amaranthCommon name: Palmer pigweed
  • Scientific name: Amaranthus palmeri
  • Grass or broadleaf: Annual broadleaf
  • Is native to the southwestern United States, has become a devastating weed problem in the South and has recently spread to the upper Midwest.
  • Most competitive and aggressive pigweed species. Season-long competition by Palmer amaranth at 2.5 plants per foot of row can reduce soybean yield by as much as 79 percent.1
  • Emerges later than many summer-annual broadleaf weeds, continues to emerge throughout the growing season and can grow 2 to 5 inches in three days or less.
  • A single female Palmer amaranth plant can produce approximately 600,000 seeds.
  • Ranked the most troublesome weed in the United States by the Weed Science Society of America (WSSA) for 2016.

A fact that may surprise you …

 The leaves, stems and seeds of Palmer amaranth are edible and highly nutritious; and the plants were once widely cultivated and eaten by Native Americans across North America, both for the abundant seeds and as a cooked or dried green vegetable.

Fast facts from Jeff Ellis, Ph.D., field scientist, Dow AgroSciences

To correctly identify Palmer amaranth when scouting, look for the following plant-distinguishing features:

  • The petioles, especially on older leaves, will be as long or longer than the leaf blade itself.
  • Plants sometimes — but not always — have a white V-shaped watermark on leaves. If a watermark is present, this rules out other members of the pigweed family.
  • Leaf shape on Palmer amaranth plants are wider than other pigweed species and ovate to diamond shape.
  • Individual plants are either male or female, which forces outcrossing and genetic diversity. This gives Palmer amaranth the ability to adapt and quickly produce resistance genes to single-mode-of-action herbicides.

Resistance statistics*

  • According to WeedScience.org, herbicide-resistant Palmer amaranth has been documented in corn and soybean fields in 24 states: Alabama, Arkansas, California, Delaware, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Michigan, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Wisconsin.
  • Since the late 1980s, Palmer amaranth has evolved resistance to six herbicide sites of action: ALS inhibitors (Group 2); microtubule inhibitors (Group 3); Photosystem II inhibitors (Group 5); EPSP synthase inhibitors (Group 9); HPPD inhibitors (Group 27); and, most recently documented in Arkansas and Mississippi, protoporphyrinogen oxidase (PPO) inhibitors (Group 14).

*Resistance confirmation does not necessarily include all weeds and may vary among different areas of each state.

Palmer amaranth control/management tips:

Ellis says:

  • In both corn and soybeans, aim to control Palmer amaranth before plants emerge by using a residual herbicide.
  • Tank-mix residual herbicides with postemergence herbicides to prevent Palmer amaranth from emerging later in the season.
  • Palmer amaranth germinates throughout the season, so it is important to “layer” residual herbicides.
  • Growers, especially for soybeans, should always use residual herbicides and avoid having to control Palmer amaranth after emergence because there are very few effective postemergence herbicide control options.

General tips to manage herbicide-resistant weeds

Growers in the Midwest and Midsouth face some of the toughest weed species, including Palmer amaranth, waterhemp, ragweed and marestail. Taking the following steps during the season can help them manage weed resistance issues:

  • Develop an integrated weed management plan that delivers multiple modes of action throughout the season. With resistance increasing, the Enlist weed control system may allow use of effective postemergence modes of action, including glufosinate in soybeans and a new 2,4-D in corn and soybeans.
  • Use full rates of the herbicides during applications. Do not use partial rates or trim back for any reason, including cost.
  • Spray when weeds are small. Although it can be challenging because of weather and other factors, this is the ideal application timing.
  • Scout fields regularly to identify weeds when they are small and easy to control.

Dow AgroSciences weed control solutions:

Corn
SureStart® II herbicide
Resicore® herbicide
Keystone® NXT herbicide
Keystone® LA NXT herbicide 

FulTime® NXT herbicide
Surpass® NXT herbicide 
Durango® DMA® herbicide
Duramax® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system

Soybeans
Sonic® herbicide
Surveil® herbicide
Durango® DMA® herbicide
Duramax® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system

Additional information:
More information can be found through these weed science resources:

Palmer Amaranth Biology, Identification and Management — Purdue University Extension

Guidelines for the Identification and Management of Palmer Amaranth in Illinois Agronomic Crops — University of Illinois Department of Crop Science

Palmer Amaranth Identified in Nine Iowa Counties — Iowa State University Extension and Outreach/Integrated Crop Management

1United Soybean Board. 2013. Palmer Amaranth Management in Soybeans. http://takeactiononweeds.com/wp-content/uploads/2014/01/palmer-amaranth-management-in-soybeans.pdf

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. FulTime NXT, Keystone LA NXT and Keystone NXT are federally Restricted Use Pesticides. Duramax, Durango DMA, Enlist Duo, FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore, Sonic, SureStart II, Surpass NXT and Surveil are not registered for sale or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore, SureStart II and Surpass NXT are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions. ©2016 Dow AgroSciences LLC